An inrush current phenomenon refers to a phenomenon in which current higher than normal current flows at the moment in which power is applied. For example, the higher current may be current several times to several ten times greater than the normal current.
FIG. 1 is a circuit diagram showing an inrush current suppressor circuit according to the related art. Referring to FIG. 1, in order to use low stand-by power, AC voltage VAC is blocked from being applied to a resistor RX,2 by using a switch SW1, thereby removing power consumption in the resistor RX,2. In addition, for the purpose of power supply for stand-by voltage VSTBY, a diode DST1, an inrush current suppressing resistor RST1, and a smoothing capacitor CIN_ST are additionally used.
In addition, a diode DInrush by-passes the inrush current of a typical boost converter so that the inrush current is prevented from flowing through an inductor Lm and a diode Do, and suppresses the intensity of the inrush current applied to a resistor RInrush1. However, current inevitably flows through the resistor RInrush1 even when the circuit of FIG. 1 is operated at a start-up mode, so that the power loss occurs at the resistor RInrush1, thereby not only exerting an undesirable influence on the whole power efficiency of the circuit, but also greatly heating parts.
FIG. 2 is a circuit diagram showing the current flow at the stand-by mode of the inrush current suppressor circuit according to the related art. Referring to FIG. 2, if the AC voltage VAC is applied at the stand-by mode, only when live potential is higher than neutral potential, current may be applied to a stand-by capacitor Cin_st through a stand-by diode Dst1 and a stand-by resistor Rst1. If the voltage is returned to the neutral potential through a rectifying part BD1 and the inrush current suppressing resistor Rinrush1, the circuit may be operated as a half-wave rectifier circuit in which the stand-by capacitor is charged. Due to the power charged in the above manner, stand-by voltage VSTBY may be generated from a stand-by power supply part STBY. In this case, since zero voltage is applied to the resistor Rx.2, power consumption by the resistor Rx.2 is not caused.
FIG. 3 is a circuit diagram showing the current flow of the inrush current suppressor circuit according to the related art when the power is started up. As shown in FIG. 3, the switch SW1 is turned on in order to change the whole circuit from the stand-by mode to the normal mode. The AC voltage VAC is applied upon the conduction of the switch SW1, so that current is applied to a start-up capacitor Co having the initial voltage of 0V. Thereafter, if a main switch M1 is turned on, a start-up power supply part MULTI is operated, so that an output voltage Vout required in the system may be generated. In this case, as current flows through the inrush current suppressing resistor Rinrush1, undesirable power consumption may be caused.
In other words, since the inrush current suppressing diode and the inrush current suppressing resistor are provided for each of the stand-by mode and the start-up mode, the number of parts may be increased, and the power consumption by the inrush current suppressing resistor may serve as a problem.